This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Parkinson's disease (PD) is a neurodegenerative disorder that affects an estimated 1 million people in the US and tens of millions worldwide and is associated with the loss of dopaminergic neurons in the substantia nigra. Dementia is common and affects approximately 40% of PD patients during the course of the disease, the risk for the development of dementia in PD being 6 times higher than in non-PD age-matched controls. Operationalized criteria to define the clinical boundaries between PD and PD with dementia (PDD) are also lacking, although this distinction may have profound clinical implications for prognosis and treatment strategies. In this study we measure T1[unreadable] in hippocampus in the brain of PD, and PDD patients and age matched control, and to determine whether T1[unreadable] values can be used in differentiating these cohorts.